Inhibitory cascade

The inhibitory cascade is a model in evolutionary developmental biology concerning the proportions of mammalian mandibular molar teeth.

Predictions

The mathematical expression used to model the inhibitory cascade is 1 + [(a - i)/i](x - 1), where a is the strength of activating developmental factors, i is the strength of inhibitory developmental factors, and x is the number of the lower molar in the tooth row (i.e. M1, M2, etc.). The M2 is always predicted to be exactly one third of the total mandibular molar area in a mammal with the typical eutherian dental formula containing three mandibular molars, with M1 = i/3a and M3 = (2a - i)/3a.[1]

Evidence

An overview of mammal species across various orders found the large majority of them to occupy either a morphospace where M1 > M2 > M3 or one where M1 < M2 < M3, concordant with the inhibitory cascade model.[2] Analysis of a broad range of Mesozoic and early Cenozoic mammaliaform taxa found that about two-thirds of them had molar ratios consistent with the inhibitory cascade's predictions, suggesting a deep evolutionary origin within Mammaliaformes for this developmental mechanism.[3]

References

  1. ^ Kavanagh, Kathryn D.; Evans, Alistair R.; Jernvall, Jukka (27 September 2007). "Predicting evolutionary patterns of mammalian teeth from development". Nature. 449 (7161): 427–432. Bibcode:2007Natur.449..427K. doi:10.1038/nature06153. ISSN 0028-0836. PMID 17898761. Retrieved 28 June 2026 – via Nature Publishing Group.
  2. ^ Polly, P. David (26 September 2007). "Development with a bite". Nature. 449 (7161): 413–414. doi:10.1038/449413a. ISSN 0028-0836. Retrieved 28 July 2026 – via Nature Publishing Group.
  3. ^ Halliday, Thomas J. D.; Goswami, Anjali (8 April 2013). "Testing the inhibitory cascade model in Mesozoic and Cenozoic mammaliaforms". BMC Evolutionary Biology. 13 (1): 79. Bibcode:2013BMCEE..13...79H. doi:10.1186/1471-2148-13-79. ISSN 1471-2148. PMC 3626779. PMID 23565593.

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